1. Field of the Invention
Embodiments of the invention generally relate to a method of electrochemical plating. More particularly, embodiments relate to a method for removing electrolyte residue from a contact ring.
2. Description of the Related Art
Electrochemical plating (ECP) has emerged as a promising process for void free filling of sub-quarter micron sized, high aspect ratio interconnect features in integrated circuit manufacturing processes. Conventional ECP systems typically plate metal ions from an electrolyte solution onto a substrate surface using a cathode contact ring to electrically contact the substrate surface. During plating, an electrical bias is simultaneously applied between the substrate-plating surface and a copper anode positioned within the electrolyte solution. The contact ring provides electrical current to the substrate surface to be plated. The application of the electrical bias causes the metal ions to be urged out of the electrolyte solution and plated onto the substrate surface.
One challenge associated with contact-type plating systems is that the electrolyte solution crystallizes or forms a solid film on the electrical contact areas when not in operation. These deposits or electrolyte residue on the contact ring, and particularly on the pins of the contact ring, can change the physical and chemical characteristics of the conductor and eventually deteriorate the contact performance resulting in plating defects. The unwanted deposits are also a source of contamination and can potentially cause damage to the substrate. For example, the deposits may bond/adhere the pins to the substrate during processing. Subsequently, the bond between the pins and the substrate must be broken to remove the substrate from the contact ring. The act of removing the substrate from the pins requires force, which may damage the substrate and may cause particulate contamination.
Efforts to minimize unwanted electrolyte buildup include covering the contact ring and the outer surface of pins with a non-plating or insulation coating. However, while insulation coating materials may prevent plating on the outer pin surface, the upper contact surface remains exposed. Thus, solid deposits are inevitably formed on the pins after extended use. Existing methods of electrolyte removal have also tried spinning a head assembly supporting the contact ring to remove the electrolyte residue using centrifugal force. Efforts also include rinsing the contact ring with water. These methods fall short of their intended purpose in that they only dry and/or dilute the electrolyte residue leaving behind crystals and/or electrolyte films on the electrical contacts and wafer contact areas. Therefore, there remains a need for a method for effectively cleaning electrical contacts and substrate contacting areas of a contact ring for ECP processes.